1. Field of the Invention
Embodiments of the present invention generally relate to downhole logging and production operations and particularly to deployment of downhole tools on non-electric cable.
2. Description of the Related Art
Costs associated with downhole drilling and completion operations have been significantly reduced over the years by the development of tools that can be deployed down a well bore to perform operations without pulling production tubing. Downhole tools are typically attached to a support cable and subsequently lowered down the well bore to perform the desired operation. Some support cables, commonly referred to as wirelines, have electrically conductive wires through which voltage may be supplied to power and control the tool.
FIG. 1 illustrates an exemplary electric downhole tool 110 attached to a wireline 120, lowered down a well bore 130. The wireline 120 comprises one or more conductive wires 122 surrounded by an insulative jacket 124. The conductive wires 122 supply a voltage signal to the tool 110 from a voltage source 140 at the surface 150. Typically, an operator at the surface 150 controls the tool 110 by varying the voltage signal supplied to the tool 110. For example, the operator may apply and remove the voltage signal to cycle power on and off, adjust a level of the voltage signal, or reverse a polarity of the voltage. The tool 110 is designed to respond to these voltage changes in a predetermined manner. As an example, an inflatable setting tool may toggle between a high volume-low pressure pump and a low volume high-pressure pump when power is cycled.
A less expensive, non-electric support cable is commonly referred to as slickline. Because slickline has no conductive lines to supply power to the attached tool, the types of the tools deployed on slickline are typically non-electric tools, such as placement and retrieval tools, mandrels, etc. Recently, battery powered tools have recently been developed for slickline operation. Operation of the battery powered tools may be initiated by lowering a slip ring device down the slickline that comes in contact with a switching device on a top surface of the tools. Alternatively, operation of the tools may be initiated by a triggering device that generates a trigger signal, for example, based upon bore hole pressure (BHP), bore hole temperature (BHT), and tool movement. Regardless of the method of initiation, the absence of electrically conductive wires prevents conventional surface intervention used to control wireline tools, which typically limits tools deployed on slickline to simple tools requiring little or no control, such as logging tools.
Accordingly, what is needed is an improved method and apparatus for operating electric downhole tools deployed on slickline.